The invention pertains to a grinding device with a grindstone for sharpening a knife, a device for adjusting the grindstone toward the knife and a control unit.
The present invention can be utilized in a series of devices with knives to be sharpened. It is, in particular, advantageous in self-contained field choppers or towed harvesting machines with chopping drums.
DE 4133043 A describes a grinding machine in which a grinding device is assigned to knives. Each cutting process is registered by a counting mechanism and the grinding process is carried out depending on the number of cuts.
U.S. Pat. No. 4,843,767, granted to Johnson on Jul. 4, 1989, discloses a grinding device for the chopping drum of a self-propelled field chopper. In this case, first and second electric motors, respectively provided for moving the grindstone to and from engagement with the knives of the chopper drum, and for sweeping the grindstone lengthwise of the chopper drum, are controlled by a system including a microprocessor and a counter which counts the number of sweeps or cycles of the grindstone and compares it to a preset threshold of the number of sweeps or cycles required to sharpen the chopper drum knives.
U.S. Pat. No. 4,834,303, granted to McClure et al. on May 30, 1989, discloses a grinding device for the chopping drum of a self-propelled field chopper. In this case, a switch, actuated by the grindstone holding arrangement once the grindstone should no longer be adjusted toward the knife due to excessive wear, is arranged in the vicinity of the end of the grindstone which faces the chopping drum. Due to this measure, the operator is informed that the grindstone, which is axially adjustable in its holder, needs to be manually adjusted closer to the knife. In addition to the costs for the switch, it is disadvantageous that the operator is only informed that the grindstone is worn out once the latter needs to be replaced.
According to the present invention, there is provided an improved grinding device.
An object of the invention is to provide a grinding device having a control unit which informs an operator of the degree to which a grind stone is worn.
A more specific object of the invention is to provide a grinding device wherein a control for feeding the grindstone towards a knife being sharpened informs the user when the grindstone is used up. This is done by storing a threshold value representing the number of feeding procedures that can be done for a certain type of grindstone before it is used up and to count either up to, or down from, the threshold value in order to obtain the signal that notifies the user when the grind stone needs to be replaced.
These and other objects will become apparent from a reading of the ensuing description together with the appended drawings.